End handler described herein is widely used in handling or transferring of a film frame in semiconductor manufacturing process.
The end handler is normally coupled to a robotic arm of a wafer manufacturing tool (such as wafer dicing tool and wafer inspection tool) to handle and transport these film frames. At this stage, finished processed whole wafers would have been attached onto film frames. The film frame consists of a rigid frame, usually made of steel, with a circular see through portion patched with a thin film where the whole processed wafer would be attached. After mounting on the film frame, these wafers on film frames would be loaded into cassettes to allow for the next stage of processing of the wafers, which could involve dicing, inspecting for defects or testing. The end handler is used to load and unload these film frames and to move one or more film frames from one position to another.
Conventionally, end handler includes at least two fingers for supporting, handling or holding an article, such as a film frame. These fingers are equipped with vacuum pads of various designs. In one conventional design, the vacuum pads consist of tiny openings on the surface of the end handler that suck against the metal frame of the film frame. In another, the vacuum pads consist of protruded vacuum pads having upward facing openings with a raised height which extends beyond the top or upper surface of the end handler to suck against the film of the film frame. In these conventional designs, when vacuum pressure is applied through the tiny openings in the vacuum pads, they purport to hold the entire film frame during handling and transportation from one point to another in the wafer processing tool.
The use of end handlers with conventional vacuum pads as described above gives rise to several problems. In the case of vacuum pads sucking against metal frame, the non-pliable metal surface of the film frames does not allow for creation of an effective vacuum seal for vacuum suction to hold down the film frame.
In the case of protruded vacuum pads, the portions of the film in contact with the protruded vacuum pads will overtime become irreversibly distended or deformed. Further, the use of protruded vacuum pads increase the overall thickness of the end handlers and increases the difficulty of it accessing a standard cassette for handling film frames. The standard film frame cassette contains up to 25 wafers, and the space between the film frames in the cassette is only between 5 mm to 8 mm. In many instances, this gap between wafers is made smaller and uneven with a smaller gap towards the centre of the film frame because of the attached wafer weighing down the film. The use of protruded vacuum pads increases the overall thickness of the end handler which makes accessing the cassette, already a very delicate operation even more so. Any mistake in its access will cause damage to the attached valuable wafers and to the end handler itself. In some cases, it may be necessary to leave alternate slots of the film frame empty to facilitate easier access of the end handler for retrieval or loading. This means that cassette would have to be re-loaded more often resulting in more down time of the automated tool. This affects overall efficiency.
However, the most important weakness of all conventional designs is that they all suffer from having weak suction force. The conventional designs involving the application of vacuum force through tiny holes on the vacuum pads (whether protruded or not) directly against the film of, or the metal frame of, the film frame which do not provide a strong enough vacuum force to hold the film frame in place. The inability to apply a large enough suction force is particularly significant when these film frames have to be moved at higher speeds. At higher speeds, without a strong or stronger vacuum force, the film frame will slide or drop off while being transported.
From the foregoing discussion, it is desirable to provide an end handler that can efficiently and speedily handle a film frame securely without any of the problems associated with conventional systems described above.